IFN-alpha is widely used for the treatment of viral infections (hepatitis B and C) and cancer, but dose-limiting toxicity has prevented many patients from benefiting from this drug. The ultimate goal of the proposed project is to develop a form of IFN-alpha that retains its anti-viral and anti-cancer effects but has little or no toxicity. Of the type I IFNs, ovine IFN-tau (oIFNtau) has been shown to exhibit high antiviral and antiproliferative activity without the toxicity associated with IFN-alpha or IFN-beta. However, because of marked sequence differences between IFN-tau and human IFNs, the former is not available for human use because of its presumed immunogenicity. Nonetheless, in vitro data from recent studies comparing a synthetic hybrid of oIFNtau and human IFN-alpha suggest that the low toxicity of oIFNtau is attributable to non-conserved amino acids present within the first 27 N-terminal residues of the mature hybrid protein. We propose to identify the critical residues and insert these residues into IFN-alpha with the goal of generating a mutant form of this cytokine that lacks the toxicity of the parent molecule. Purified proteins generated from the mutant genes will be assayed for their ability to inhibit viral replication and tumor cell growth. Also, the level of cytotoxicity mediated by these proteins will be examined on a panel of normal human cells. If this project is successful, the analogs developed should be able to be used in much higher doses and with greater efficacy than native IFN-alpha. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE